Triggering factors are events or conditions that cause psoriasis to flare up or worsen.
Skin injury. Injury or trauma can make psoriasis worse. This feature of the disease is called the Koebner phenomenon. Patches of thick, flaky skin may appear following a burn, graze, or rash. If someone is prone to outbreaks of psoriasis, it is important to promptly treat rashes such as those caused by allergies to medication. Otherwise, the rash could lead to a flare-up of psoriasis.
The Koebner phenomenon occurs in about one in every four people with psoriasis. Why it happens is not known. It occurs most frequently in people who develop psoriasis early in life (before age 15).
Climate change. Lengthy exposure to a dry climate with low relative humidity can make psoriasis worse. For many people, sun exposure during the summer helps to clear psoriasis. However, people who are sun-sensitive find that psoriasis flares up when skin is exposed to the sun.
Infection. Strep throat can lead to guttate psoriasis in children and young adults. Anyone with psoriasis who gets strep throat should be treated promptly with antibiotics to prevent a flare-up of psoriasis.
HIV infection can cause psoriasis to flare up or to appear for the first time. Severe forms of psoriasis, such as inverse psoriasis, become more common as HIV infection progresses and the immune system becomes weaker.
Drug reactions. Certain medications may make psoriasis worse. These include lithium (prescribed to treat bipolar disorder), beta blockers (prescribed for heart problems), anti-malarial drugs, and nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (available by prescription or over the counter for pain relief).
NSAIDs are often used to treat psoriatic arthritis. In such cases, the benefits and risks of treatment need to be carefully assessed. Flare-ups of psoriasis caused by NSAIDs usually respond to treatment. Abuse of alcohol, on the other hand, can make psoriasis treatment ineffective.
Stress. Severe emotional stress may play a role in the appearance of psoriasis or in flare-ups of the disease. However, the impact of stress can be difficult to assess. Techniques to reduce stress can be helpful if flare-ups of psoriasis follow a pattern and stress factors can be recognized as part of that pattern.